1. Field of the Invention
The present invention relates to a speaker unit to be incorporated in a small-sized electronic device such as a portable telephone, digital camera, etc.
2. Description of Related Art
Disk-type speaker units using a circular diaphragm have been conventionally a mainstream of such a kind of speaker unit (see JP 2004-48223, A), while track-type speaker units using a diaphragm in an elliptical shape or a track shape with an aspect ratio exceeding one have been developed in recent years (see JP 2000-350286, A).
In a track-type speaker unit 4 shown in FIG. 16 to FIG. 20, for example, a diaphragm 6 with an aspect ratio exceeding one and a drive mechanism 7 including a coil 71 for driving the diaphragm 6 are provided, as shown in FIG. 16 and FIG. 17, in an internal space of a frame 41 made of a synthetic resin. As shown in FIG. 17, a pair of air holes 42, 42 opening on a rear surface opposite to a sound-emitting surface 40 are provided at both ends in a longitudinal direction of the frame 41. Each of the air holes 42 is covered with a mesh sheet 8.
Furthermore, as shown in FIG. 18 to FIG. 20, a pair of electrode members 5, 5 for externally supplying power to the coil 71 are attached to the vicinity of the mesh sheet 8 covering the pair of air holes 42, 42 at the both ends in the longitudinal direction of the frame 41. Each of the electrode members 5 is made of a sheet metal, and includes a clamping portion 51 with a U-shaped cross section for clamping an end of the frame 41 and being fixed to the end, and an elastic arm portion 52 extending from the clamping portion 51 inclined against the rear surface of the frame 41.
FIG. 21 illustrates a process of attaching each of the electrode members 5 to the frame 41. As shown, each clamped portion 43 is provided at either end in the longitudinal direction of the frame 41. An adhesive is applied to any one of three inner wall surfaces forming the clamping portion 51 of the electrode member 5, and then the clamping portion 51 is fitted into the clamped portion 43 of the frame 41. As a result, the electrode member 5 is bonded and fixed to the frame 41 with the clamping portion 51 of the electrode member 5 clamping the clamped portion 43 of the frame 41. Thereafter, a pair of conductors (not shown) led from the coil 71 of the drive mechanism 7 shown in FIG. 17 are each soldered to the clamping portion 51 of the electrode member 5 to complete assembly of the speaker unit 4.
In a process of incorporating the speaker unit 4 thus assembled into an electronic device such as a portable telephone or the like, as shown in FIG. 15, the speaker unit 4 is placed as opposed to a sound-emitting opening 13 of one case half 1 of a casing, and thereafter the case half 1 and the other case half 11 are joined to each other with a circuit board 12 held therebetween.
As a result, the electrode member 5 of the speaker unit 4 is press-contacted with a pad (not shown) formed on a surface of the circuit board 12 to produce an electrical connection between the circuit board 12 and the speaker unit 4. In this state, the elastic arm portion 52 of the electrode member 5 elastically deforms as shown in FIG. 22, and an elastic return force thereof maintains the press-contact of the elastic arm portion 52 to the pad.
However, in the conventional speaker unit 4, the electrode member 5 elastically deforms as shown in FIG. 22 due to the assembling process shown in FIG. 15, and comes close to a rear surface 44 of the frame 41. Consequently, the air hole 42 shown in FIG. 17 is slightly closed by the elastic arm portion 52 of the electrode member 5.
Especially, the speaker unit 4 in recent years has been made thinner, so that the elastic arm portion 52 of the electrode member 5 deforms to a posture approximately parallel to the rear surface 44 of the frame 41. Consequently, space between the electrode member 5 and the frame 41 becomes smaller and smaller, which makes an air flow accompanying a sound of the speaker unit 4 poorer. Accordingly, there has been a problem that expected low-frequency acoustic characteristics cannot be obtained.
In the conventional disk-type speaker unit, the above problem can be relatively easily solved by staggering a position of the air hole of the frame and a position of the electrode member. However, it is difficult in the track-type speaker unit to stagger a position of the air hole of the frame and a position of the electrode member because of design constraint on the position of the air hole of the frame.